Kitchen sink water coming out the backyard stucco

[Handygal11]

I noticed that our kitchen sink was getting clogged up and when I went to the garage, there was a puddle of water coming from the wall so when I went outside to the backyard, you could see water leaking from the stucco and there’s corrosion and a hole where the stucco has disintegrated . I then went back to the kitchen and looked in the cupboard on the side of the sink and there is a lot of black mold but underneath the sink is not wet.